View Full Version : prop pitch decisions....HELP!

05-01-2001, 04:45 PM
I'm trying to decide if I should keep running my 24 Chopper @ 6900 r's, or move up to a 26 or 28 pitch wheel. The boat in question is a 21' Checkmate Starflite with 5.5" of set-back. Motor is a '93 2.5/245 w/ stock gearcase and no cone. I was told these motors are reliable up to 7K r's. However, I was hoping to knock off a few hundred r's with a bigger wheel(and hopefully pickup some MPH). Top speed with the 24 Chopper is 71mph @ 6900. Am I correct in assuming that I could go to a 26 pitch wheel and run 73 @ 6700, or a 28 wheel and run 75mph @ 6500 r's? Would 6500 r's be "lugging" this motor down? I plan on 4 more inches of setback, so I can run the prop up a bit higher. What pitch wheel would be the best for top-end on this set-up? Would a 3 blade or 4 blade be better?


05-02-2001, 10:29 AM
Just my opinion but...

The 2.5 Merc high performance carb motor was rated 245 HP at 7500 RPM. HP stayed strong way up in the 8000 RPM range. Why would you want to run the motor below peak HP RPM? And if you did run below peak HP RPM, why would you think it will go faster? Running the motor 8000 for short bursts (1/4 mile maybe 1/2 mile) will not hurt it. If your plan is to hold the pedal down for miles and miles, you need a new plan!

You are on the right track with the idea of more set-back. Set the motor back, jack it up and prop it to turn at least 7500 RPM with your "normal" load. Light load with low fuel let it go to at least 8000 RPM. Lugging an outboard is the best way to kill them.

The Merc 14.5 inch dia. Chopper II, 3 blade is tough to beat on a hull like the C'mate.

Have fun & be safe!


05-02-2001, 10:33 AM
i personally like the mazco re3 in a 26 or 27 pitch and jacking the motor up should let you spin it up to your rpm.running a 26 on my starflite and after tryig dozens of props the mazco seemed to be the best wheel for my rig.